fix: build failure with ninja and Python 3 on Windows

[zcbenz]

There are a few python code not updated to support python 3, the code path seems to only run when using ninja on Windows.

[targos]

ldxx_host is also referenced in the other branch and it doesn't seem to be an issue (I always use ninja on unix systems)

[zcbenz]

Python 3 fails with this error here:

Traceback (most recent call last):
  File "node/tools/gyp/gyp_main.py", line 45, in <module>
    sys.exit(gyp.script_main())
  File "node/tools/gyp\pylib\gyp\__init__.py", line 662, in script_main
    return main(sys.argv[1:])
  File "node/tools/gyp\pylib\gyp\__init__.py", line 654, in main
    return gyp_main(args)
  File "node/tools/gyp\pylib\gyp\__init__.py", line 639, in gyp_main
    generator.GenerateOutput(flat_list, targets, data, params)
  File "node/tools/gyp\pylib\gyp\generator\ninja.py", line 2936, in GenerateOutput
    target_list, target_dicts, data, params, config_name
  File "node/tools/gyp\pylib\gyp\generator\ninja.py", line 2393, in GenerateOutputForConfig
    master_ninja.variable("ldxx_host", ldxx_host)
UnboundLocalError: local variable 'ldxx_host' referenced before assignment

And that is because ldxx_host has never been declared for Windows:
https://github.com/nodejs/gyp-next/blob/main/pylib/gyp/generator/ninja.py#L2235-L2250

Since ldxx_host is never used on Windows, I think removing this line would be a reasonable fix.

[gengjiawen]

@targos Since the code part is in block if flavor == "win", I guess it's okay ?

@zcbenz Out of curiosity, do you successfully build Node.js using Ninja on windows ?

[zcbenz]

Out of curiosity, do you successfully build Node.js using Ninja on windows ?

Yes, but it requires some patches:
https://github.com/yue/node/commits/node-16.4.0

(It is used in a modified version of Node: https://github.com/yue/yode)